Whoever said Japanese people are shy has never dipped a toe in an onsen, a natural hot spring where nudity reigns supreme. For thousands of years, residents have dropped trou in these natural oases. According to legend, ancient villagers spotted injured animals soaking in the warm waters, so they followed suit. Today, there’s even a phrase—hadaka no tsukiai (naked friendship)—which refers to bonding while bathing together.
In order to qualify as an onsen, a hot spring must be more than 25 C and contain at least one of 19 minerals approved by the official Japanese Onsen Law. The substances range from radium to sulphate, giving the water healing properties said to aid everything from dermatitis to arthritis. There are more than 3,000 onsen dotting the Japanese countryside, with options for everyone—from the easily embarrassed to uninhibited naturists.
Gunma prefecture is home to more than 100 springs, but Kusatsu may be its most spectacular. Set in a mountain village, the hot spring is famous for the amount of water it produces—about 32,000 litres every minute—and its heat, which tops 60 C. It’s so hot that it must be cooled by “beaters”, staff who rhythmically flap large wooden panels, keeping in sync with traditional song. The village has a number of communal onsen—including 19 with free entry.
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In contrast to Kusatsu, Kita is still relatively unknown and very traditional. Access the onsen on foot, about 400 metres down a slope from the nearest parking lot. According to local legend, a tengu (a fearsome supernatural creature) discovered the springs over 1,200 years ago—which helps explain the grimacing tengu masks adorning the place. Most of the baths are mixed gender, but there are still men- and women-only options.
For a more intimate experience, book a private onsen in a ryokan (traditional inn). Located in the Shuzenji hot spring area, about two hours by train from Tokyo, Yagyu-no-Sho ryokan offers the best of both worlds: communal and private onsen. Each suite features a luxe outdoor deck with a private bath. After a long soak, savour a 10-course meal in your suite, served by your personal hostess. The two communal onsen are made of natural rock, surrounded by maple trees, and are assigned at different times to men and women.